【作者】 黄玲玲；

【导师】 彭镇华；

【作者基本信息】 中国林业科学研究院 ， 森林培育学， 2009， 博士

【摘要】 氮和磷是陆地水体的重要污染物,相邻农田中的氮和磷经非点源途径通过河岸带进入水体。河岸带是高地和水体之间的过渡带,健康的河岸带系统能够通过物理的、生物的和生物化学的过程,实现对氮磷的截留和转化。本文以四川省长宁县淯江河流域竹林河岸带为研究对象,对相邻的农田和竹林河岸带进行了系统观测,从河岸带的植被、土壤特征、水文过程以及河岸带宽度等四个方面,探讨了竹林河岸带对氮磷的截留转化作用。主要结论如下:(1)竹林河岸带的植物隶属于30科44属45种,主要竹种为硬头黄竹。其中:蕨类植物4科4属4种,被子植物26科40属41种。植物科属组成以单属科为主(20科),占总科数的66.67%。群落垂直结构分化较明显,群落乔木层、灌木层及草本层共有40个种群,其分布格局有聚集分布、均匀分布、聚集/随机和随机/均匀分布四种类型,且以聚集分布为主要格局类型。(2)在竹林河岸带中,每公顷硬头黄竹林总生物量为96.559t;其中秆为75.788t,占78.49%;枝为7.533t,占7.80%;叶为4.989t,占5.17%;根为1.460t,占1.51%;蔸为6.789t,占7.03%。各个器官N、P元素密度分别由大到小排序:叶>根>蔸>枝>秆,叶>根>枝>蔸>秆。5m宽的竹林河岸带林分N储存量为982.4 kg·hm-2,高于40m宽的竹林河岸缓冲带林分N储存量的30.86%。5m宽的竹林河岸带硬头黄竹林分磷元素储存量为190.1 kg·hm-2,高于40m宽的竹林河岸带林分磷元素储存量的30.83%。5m宽的硬头黄竹林每公顷N、P储存最大,10m、20m、30m、40m宽的硬头黄竹林每公顷N、P储存量分别为5m宽的88.65%、83.85%、79.04%、76.42%。(3)竹林河岸带土壤的理化性质。在土壤剖面0～100cm土层中,土壤容重的变化范围为0.959～1.669g/cm3,土壤越深,土壤容重越大。土壤的机械组成变化很大,农田处的粘粒超过20.41%,而竹林河岸带沿河边的土壤已表现出砂土特征。土壤pH值均以接近农田的最高为6.12,宽度超过20m后,土壤pH值就明显降低。不同宽度不同层次的土壤有机质含量为14.45～36.13g/kg。土壤全氮浓度变化范围为821.20～1900.20mg/kg,土壤表层的土壤全氮浓度最高,为1900.2mg/kg,土层越深土壤全氮浓度越低。土壤碱解氮浓度为58.00～118.82mg/kg。土壤速效磷浓度为6.83～28.86mg/kg,土壤表层的速效磷浓度最高,为28.86mg/kg。(4)不同宽度的竹林河岸带土壤水的TN、TP浓度均以接近农田的最高,20m宽的硬头黄竹林河岸带,土壤水的TN浓度降低40.53%、TP浓度降低85.07%。从竹林河岸带土壤对N、P的吸附储存转化效率来看,20m宽的硬头黄竹林土壤水全N、碱解N和速效P的截留率达到了11.16%、56.93%和41.33%,30m宽的硬头黄竹林对土壤水全N、碱解N和速效P截留率达到了58.30%、69.67%和43.75%,40m宽的硬头黄竹林土壤水全N、碱解N和速效P截留率达到了37.20%、61.82%和69.45%。(5)该研究区域雨季不是十分明显。在竹林河岸带的林内,2008年全年林内穿透雨为702.2mm,林冠截留为229.6mm,分别占全年降雨量的72.14%、23.59%。竹林河岸带年树干茎流为41.5mm,占全年降水量的4.26%。农田对竹林河岸带的水量输入较大,且不同季节变化幅度较大,并以地表水和20cm深的土壤径流为主,一年100m长的农田剖面四个层次共流出水量6221L。每年通过穿透雨输入林地的TN和TP分别是53.2kg·hm-2和0.420 kg·hm-2。其中,NH4+-N 28.3 kg·hm-2,占总氮量的53%;NO3--N 23.1 kg·hm-2,占总氮量的43.4%;PO43--P的输入量是0.219 kg·hm-2,占总磷的52%,;每年通过树干茎流输入林地的TN和TP分别是3.32 kg·hm-2和0.101 kg·hm-2,其中NH4+-N为1.76 kg·hm-2,NO3--N为1.41 kg/hm2,PO43--P是0.042 kg·hm-2。竹林河岸带穿透雨输入林地的氮约为树干茎流输入氮的16倍,穿透雨输入林地的磷约为树干茎流输入磷的4倍。由于农田的施肥,100米长的农田土壤剖面一年从土壤四个层次共输入竹林河岸带的TN 108.66g,NO3--N 76.62g,NO2--N 5.42g,NH4+-N 22.58g;TP 0.459g,PO43--P 0.263g,是河流和河岸带氮磷的主要输入源。(6)以100m长的土壤剖面计算,农田每年通过径流流入河流和竹林河岸带的水量6221L,其中土壤表层流入3340L,占输入量的53.69%。5m宽的竹林河岸带通过土壤径流流入河流的水量4485L,比农田减少了27.91%,其中土壤表层输入2580L,占输入量的57.53%。10m宽的竹林河岸缓冲带通过土壤径流流入河流的水量3772L,比农田减少了39.37%,其中土壤表层输入2145L,占输入量的56.87%。20m宽的竹林河岸带土壤径流水量减少了40.72%,30m、40m宽的土壤径流水量分别减少了39.75%和46.39%。以上可以看出,10m宽竹林河岸带就可以有效截留土壤水。除此之外,土壤水TN、TP、NO3--N、NO2--N、NH4+-N、PO43--P的浓度也显著受河岸带宽度影响,10m宽的竹林河岸带土壤水TN、TP、NO3--N、NO2--N、NH4+-N、PO43--P的浓度比农田分别降低了17.90%、82.32%、16.29%、33.07%、33.67%和69.49%;20m宽的竹林河岸带土壤水TN、TP、NO3--N、NO2--N、NH4+-N、PO43--P的浓度分别降低了40.53%、84.53%、43.15%、51.39%、47.82%和75.14%;30m宽的竹林河岸缓冲带土壤水TN、TP、NO3--N、NO2--N、NH4+-N、PO43--P的浓度降低了40.85%、88.95%、34.94%、67.20%、73.23%和78.81%;40m宽的竹林河岸带土壤水TN、TP、NO3--N、NO2--N、NH4+-N、PO43--P的浓度变化与30m宽的差别不大综上所述,通过植物吸收转化、土壤截留、减少土壤水输出等物理的、生物的和生物化学的过程,20~30m的竹林河岸带可以有效降低相邻农田氮磷等营养元素通过非点源途径向河流的输入,从而达到减轻河流非点源污染的目的。在此基础上,对目前我国河岸带研究中存在的问题进行了讨论,并对我国开展河岸带的研究提出了建议。更多还原

【Abstract】 Farmland nitrogen and phosphorus can enter adjacent water body via erosion and leaching, being the important pollutants in terrestrial water bodies. Riparian buffer zone is a transitional zone between highland and its adjacent water body, and a healthy riparian buffer zone can retain and transform the incoming N and P through physical, biological, and biochemical processes. In this paper, Yu Jiang River in Changning county, Sichuan province being the study object, a series of observation about the bamboo buffer zone and its adjacent farmland were done, such as vegetation features, soil characters, hydrological processes and the buffer zone width. The factors governing the N and P retaining and transformation were analyzed.(1) The vegetation in the bamboo buffer zone belongs to 45 species, 44 genera, 30 families, and the uppermost is Bambusa rigida Keng et Keng f., including 4 species of ferns, 41 species of angiosperms. The vertical structure distribution of plant community is obviously, there are 40 populations of trees, shrub and herb layers in total. And 4 types of distribution pattern, aggregated distribution, self distribution, aggregated/random distribution and random/self distribution. Aggregated distribution was the main types of the most population. From the diameter distribution of trees layers, diameter distribution curve is on the right side, most of the trees diameter is the large and central scale.(2) In bamboo buffer zone, the biomass of Bambusa rigida is 96.559t/hm2. The biomass and proportion among stem, branch, leaf, root, stump were 75.788t, accounting for 78.49%; 7.533t, accounting for 7.80%; 4.989t,accounting for 5.17%; 1.460t,accounting for 1.51%; 6.789t,accounting for 7.03%. At the different ages level, stem, root and stump got weight with the increasing age, the weight of branches and leaves reach maximum at the second year .Bambusa rigida plays an important role on absorption, reserving, transforming N and P. Put the organs content of N,P in descending order, the highest content is leaf for N, and then root, stump, branch and stem. While the highest content is also leaf for P, and then , root, branch, stump, and stem. Bambusa rigida forest N reserves exist an certain difference through the different width bamboo riverside buffer strips.5 meters wide could reserve 982.4kg/hm2,higher than 40 meters by 30.86%. With the increasing buffer strips width, the Bambusa rigida forest N reserves are decreasing. P reserves also exist an certain difference,5 meters wide could reserve 190.1kg/hm2,higher than 40 meters by 30.83%. With the increasing buffer strips width, the Bambusa rigida forest P reserves are also decreasing.(3) The soil physical and chemical characters of bamboo buffer zone are introduced. Soil bulk density changes from 0.959 g/cm3 to 1.669g/cm3 through surface to 100cm deep of soil. Widely changes on the content of soil, 20.41% of soil is clay and half is sand beside agricultural, while with the transition from agricultural to river, the content of the soil became the characteristic of sand. The value and order is not obviously among different levels and width, it means the soil structure and stability of bamboo riverside buffer strips is on a high level. Soil pH value is highly 6.12 close to agricultural, when the width becomes more than 20m, the soil pH value significantly decreased. Soil organic content changes from 14.45 g/kg to 36.13g/kg among different width and different levels. The soil total N changes from 821.20 mg/kg to 1900.20mg/kg, the soil surface total N content is highest for 1900.2mg/kg, the deeper of the soil, the lower content of the total N. The content of available N changes from 58.00mg/kg to 118.82mg/kg. The content of available P changes from 6.83mg/kg to 28.86mg/kg, the soil surface available P is highest for 22.86mg/kg.Above all, the content distribution of N, P in bamboo forest is impacted on agricultural fertilizer, rainfall, branch and leaf of Bambusa rigida forest.(4) The TN content of different levels had a big difference, while the different width at the same level is not obviously. The TN content of soil water is the highest close to the agricultural. With the increasing buffer strips width, soil water TN content is decreasing. when the width is wider than 20 meters, the tendency of soil water TN content is reducing,20 meters wide buffer strips could reduce 40.53%.The soil water TP content had the similar regular, the more wide buffer zone, the more N, P element are retained by bamboo forest, and reduced the soil water TN, TP content. Above all, 20 meters wide bamboo riverside buffer strips could reduce TP content 85.07%. From retaining and transformation efficiency by buffer zone soil, 20 meters wide Bambusa rigida forest intercepted efficiency to total N, alkaline N and available P is 11.16%, 56.93% and 41.33% respectively, 30 meters wide Bambusa rigida forest intercepted efficiency to total N, available N and available P is 58.30%, 69.67% and 43.75% respectively, 40 meters wide Bambusa rigida forest intercepted efficiency to total N, alkaline N and available P is 37.20%, 61.82% and 69.45% respectively. From the different width Bambusa rigida forest riverside buffer strips to see intercepted efficiency of total N, alkaline N and available P,30 meters wide bamboo riverside could intercept most N, P effectively.(5) The monsoon of this area is not obviously, penetrate water and tree crown interception of bamboo riverside buffer strips is 702.2 mm and 229.6mm respectively in 2008. The proportion of the whole year precipitation is 72.14% and 23.59%. Total N of penetrate water through one year is 53.2 kg·hm-2, while NH4+-N and NO3--N is 28.3 kg·hm-2 and 23.1 kg·hm-2, the proportion of them is 53% and 43.4% respectively. Total P of penetrate water is 0.420 kg·hm-2, PO43--P took up 52% of TP which is 0.219 kg·hm-2. Total N of stem runoff through one year is 53.2 kg·hm-2, while NH4+-N and NO3--N is 1.76 kg·hm-2 and 1.41 kg·hm-2,the proportion of them is 53% and 42% respectively. Total P of penetrate water is 0.101 kg·hm-2, PO43--P took up 40% of TP which is 0.042 kg·hm-2.Totle N of penetrate water is 16 times the size of the stem runoff, while for Total P is 4 times. For agricultural fertilizer, TN, NO3--N, NO2--N, NH4+-N, TP, PO43--P which were brought to bamboo riverside buffer strips from agricultural were 108.66g, 76.62g, 5.42g, 22.58g, 0.459g, 0.263g respectively for 100m long through one year. It’s the main source of N and P in riverside.(6) Being computated by the 100 meters soil profile, waters from the agricultural flows into the rivers and bamboo riverside buffer strips are totally 6221L every year. The soil surface flows into 3340L, accounts for 53.69%. Waters through 5 meters buffer strips flows into the rivers are totally 4485L, reduced 27.91% compared to the farmland, the soil surface flows into 2580L,accounts for 57.53%.Waters through 10 meters buffer strips flows into the rivers are totally 3772L,reduced 39.37%, the soil surface flows into 2145L, accounts for 56.87%.To sum up, through the physical, biochemical and biological processes of plant absorption, reservation, soil retaining, reducing the soil water input, 20~30m bamboo buffer zone can reduce N, P element input to Yujiang river, so as to achieve the purpose of reducing non-point source pollution. The problems existing in riparian buffer zone study were discussed, and some suggestions for the further study in China were presented.更多还原